GB2148340A

GB2148340A - Encapsulated bleach composition and method of preparation

Info

Publication number: GB2148340A
Application number: GB08426037A
Authority: GB
Inventors: Charles Elwood Jones; Mark Anthony Weiss
Original assignee: FMC Corp
Current assignee: FMC Corp
Priority date: 1983-10-17
Filing date: 1984-10-15
Publication date: 1985-05-30
Also published as: DK161389B; DK493884A; SE8405161D0; FI843865L; FI843865A0; FI78513C; NO164043C; SE456090B; NO844124L; GB8426037D0; DK493884D0; FI78513B; GB2148340B; DK161389C; SE8405161L; NO164043B; CA1223404A; US4526699A

Description

1

SPECIFICATION

Encapsulated bleach composition and method of preparation GB 2 148 340 A 1 This invention relates to solid available halogen bleaching compositions which minimize localized fabric damage, and in the case of colored fabrics, also minimize localized dye attack.

It is well known that solid available halogen bleach compositions when used during laundering can cause fabric damage as well as localized dye attack on colored fabrics. These problems are particularly prevalent when the formulation containing the bleach composition is either added to a load of dry laundry or added into a clothes washer during its filling cycle.

In addition, when available halogen bleaching agents are formulated into a laundry detergent, some of the organic components such as surfactants and perfumes, can react with the halogen to cause a decrease in available chlorine and general cleaning effectiveness. These and other deficiencies of N-halo bleach compositions are summarized by Brubaker in U.S. Patent No. 4,279,764. Brubaker teaches the incorporation of an N-H chlorine-accepting compound into a silicate-bound, hydrated soluble salt coating. Such N-H chlorine-accepting compounds, although effective, add to the cost of a bleach formulation and decrease the overall efficacy of the bleach or detergent compared with a formulation absent said N-H compound.

Encapsulation of calcium hypochlorite products is taught by Saeman et al in U.S. Patent No. 4,048,351 using molten, hydrated inorganic salts as a means to prevent dusting and to resist degradation by organics.

The process of Saeman et al, while useful for coating alkaline inorganic hypochlorites, is not known to be 20 applicable to organic N-halo compositions nor to produce a product useful to prevent fabric and dye attack.

In accordance with the present invention, there is provided an Whalo bleach composition which minimizes both local dye attack on colored fabrics and localized fabric damage. The composition comprises particles of a halogen bleaching agent having at least one Whalo atom capable of releasing a hypohalite ion to an aqueous solution, such particles being coated with a sufficient quantity of a soluble hydrated silicate-bound 25 inorganic salt in admixture with a soluble, alkali metal salt of boric acid so that the ratio of the Whalo atoms to the boron atoms range from about 0.5:1 to about 10: 1.

The alkali metal salt of boric acid serves as a coating aid for encapsulating the N-halo bleaching agent and also, but unexpectedly, appears to control or mitigate the hypohalite ion formed by contact of the N-halo bleaching agent with the aqueous solution. This mitigating eff ect further decreases the possibility of 30 localized dye atttack and fabric damage. In addition, the presence of the alkali metal salt of boric acid enhances the detergency of the laundry wash water.

Although alkali metal salts of boric acid have been used to form dry borate-hypochlorite compositions by Stephanou et al in U.S. Patent No. 2,977,314, no such control or mitigation effect was observed. However, the present invention diff ers substantially in composition from the teaching of Stephanou et al and the alkali 35 metal salt of boric acid is used for a different function by Stephanou et al.

It is well known that the anion formed by dissolving an alkali metal salt of boric acid is dependent on the pH of the solution. Therefore, one skilled in the art will recognize that any alkali metal salt of boric acid may be used to practice the present invention. Desirably, the alkali metal cation will be one of the more available alkali metals, such as lithium sodium, and pottasium.

For economy, it is preferable thatthe boric acid salt used in the practice of this invention contain a sodium cation. Suitable sodium salts include, but are not limited to, disodium tetraborate pentahydrate, disodium tetraborate tetrahydrate, disodiurn tetraborate, sodium pentaborate pentahydrate, sodium metaborate tetrahydrate, sodium metaborate dihydrate, and disodium octaborate tetrahydrate or mixtures thereof.

The N-halo compound is desirably an N-chloro compound although N-bromo and N-iodo compounds may 45 be preferred where optimum germicidal activity is desired. Normally, the N-chloro compounds will be an oxidant of the type which releases chlorine under detergent bleaching conditions, such as potassium dich loroisocyanu rate, sodium dichloroisocyanurate and hydrates, as well as other N-chloro compounds, such as those disclosed in U.S. Patent No. 4,279,764.

Suitable hydratable inorganic salts are sodium carbonate, trisodiurn phosphate, disodium phosphate, 50 sodium sulfate and condensed polyphosphates, such as Na4P2O7 and Na5P3010; partial hydrates of these salts can also be used.

The alkali metal silicate encapsulating liquid is conveniently a sodium silicate solution having a Si02/Na2O ratio offrom about 3.2:1 to about 2.4:1 and a total solids content of from about 1.0-50%. Preferred solutions contain 20-35% solids with a Si02/Na2O ratio offrom about 2.8:1 to about 3.2: 1. The encapsulated bleach 55 product may include inert ingredients, such as sodium alumina silicates, sodium sesquicarbonate, sodium bicarbonate, sodium chloride, silica flour, and salts of organic acids.

The preferred ratio of N-halo atoms to boron atoms in the composition will vary according to the degree of chlorine mitigation and detergency desired in the solution, as well as the concentration of hypohalite ion desired in the solution. Normally, when an available chlorine compound is used in laundry wash or rinse water, a concentration of 10 to 200 milligrams per litre (mg/1) available chlorine is desirable. The preferred range is 15 to 150 mg/I as this concentration is the most effective use level of a chlorine bleach agent.

is 2 GB 2 148 340 A 2 It has been found that the ratio of N-halo atom to the boron atom in the composition is desirably from about 0.5:1 to about 10: 1. A ratio of less than 0.5:1 may be used but at a sacrifice in economy as a large quantity of the composition is required to attain the desired available chlorine concentration. A ratio above 10: 1 provides insuff icient mitigation to protect againstthe localized dye attack; a ratio of from 1: 1 to 5: 1 is preferred as it includes the most economical, effective, and safe range.

The encapsulated halogen bleach product herein is prepared in the known manner of applying a silicate-bound, hydrated salt coating to particulate halogen bleaching agents. Generally, such a procedure, commonly referred to as agglomeration, involves contacting finely-divided, soluble anhydrous inorganic salt with aqueous alkali metal silicate in the presence of the halogen bleach particles while maintaining some form of agitation. On contactwith the aqueous silicate, the anhydrous salt undergoes hydration to give hydrated salt particles which are bound together by the silicate into agglomerates containing embedded bleach particles.

Agglomeration of the solids aforesaid may be accomplished by spraying the solids with a mist of the silicate solution during agitation. The contacting may also be effected by pouring or dripping the liquid onto the solids. Whichever waythe contacting is carried out, the solids should be constantly in motion so there is 15 intimate contact between the solid particles and the agglomerating silicate solution. Moving beds, which have been found satisfactory, include such well-known devices as paddle and blade-type mixers, rotating drums, and inclined discs. The agglomerated product is then dried either in vacuum or in air. Preferably, the product is dried at a temperature of about 20'C to 50'C afterwhich it can be packaged as such or added to a detergent formulation. Although a single coating on the N-halo bleaching agent is sufficient for most applications, at least one additional coating may be desirable. The second coating may consist of an alkali metal silicate alone, particularly when the composition is intended for use with delicate fabrics. The added alkali metal silicate coating can provide further hydration and additional silicate for binding the hydrated salt.

One familiar with the art will recognize that it is desirable that the mean particle size of a compound used for the coating is smallerthan the mean particle size of the N-halo compound to minimize the quantity of coating compound required.

Although the encapsulated bleaches prepared in accordance with the invention can be added to the wash solution, they are conveniently introduced as a component of the detergent or soap formulation. Suitable formulation and ingredients are disclosed in U.S. Patent No. 4,279,674, which is incorporated herein.

Such formulations will comprise by weight, from about 5% to about 50% of the herein bleach system, from 30 about 5% to 50% of the detergent agent, and optionally, from about 1% to 60% of a detergency builder, which can also function as a buffer to provide the requisite pH range when the composition is added to water.

The compositions herein can include detergent adjunct materials and carriers commonly found in laundering and cleaning compositions. For example, various perfumes, optical brighteners, fillers, anti-caking agents, fabric softeners, and the like, can be present to provide the usual benefits occasioned by 35 the use of such materials in detergent compositions. Enzymes, especially the thermally stable proteolytic and lipolytic enzymes used in laundry detergents, also can be dry-mixed in the compositions herein.

The examples which follow are presented to illustrate the best mode of practicing the invention but are not to be construed to limit the invention to the examples. For convenience, the examples are described in terms of sodium d ich I oroisocyanu rate clihydrate as the N-halo compound, with a sodium carbonate as the 40 hydratable salt, and using a commercial sodium silicate liquid with a silica to sodium oxide ratio of 3:22 containing 28.7% silica.

The following tests were used to evaluate the compositions:

Localized dye attack test Localized dye attack was tested by placing a 3 gram sample of a chlorine-containing detergent (generally 1.12% available chlorine) between 2 prewashed swatches of 100% cotton denim (15 x 15 cm) in a one litre beaker. A 500-600 ml portion of water was then added to the beaker and the beaker allowed to stand for 90 seconds at 35'C-40'C. A numerical rating system was designed to record the extent (area) and intensity (color change) of the bottom swatch. To record the area affected, a transparent grid of 5 mm squares was placed over the swatch and a number of squares with visible attack counted. Over 70 yielded a one rating; 50- 69, a two rating; 30-49, a three rating; 10-29, a four rating; and less than 10, a five rating. Intensity measurements were more subjective, but again a five rating was given to the most desirable (no visual change) and lower ratings to more intense dye attack. Data is reported as the average of the intensity and extent rating. The detergent formulation had the following compositions: Sodium Tripolyphosphate: 22% Surfactants: 17% Sodium Sulfate: 38% Sodium Carbonate: 2% SilicateSolids: 10% Carboxymethyl Cellulose: 1% Moisture: 10% 3 GB 2 148 340 A 3 Tea stain removal test Terg-O-TometerTm tests were performed using detergent solutions prepared as above containing 1.5 g/1 of detergent powder and a 16 and 32 mg/1 available chlorine. These formulations were compared to each other and to a control formulation of 1.5 g of the detergent powder. The temperature was 4WC (1 05'F) using hard water (68 and 136 mg/I hardness) and a washing time of 15 minutes. The tests were performed on cotton and cotton polyester blend (10 x 12.5 cm) swatches that had been stained with tea and heat set in a clothes dryer for 45 minutes prior to rinsing. Stain removal was reported as the change in the whiteness index (LWI) of the swatches. This is found by taking the L, a, and b, readings from a Hunter D25 ReflectometerTm before and after washing and applying them to the following equations:

WI = L + 3 (a-b) L\WI = W' after - WI before Example 1

A dry mix was prepared containing 244.8 g anhydrous sodium carbonate, 133. 4 g sodium dichloroisocy anurate dihydrate (NaDCC.2H20) and 66.3 g disodiurn octaborate tetrahydrate in a rotary mixer/ agglomerator 8 inches in diameter with four flights normal to the shell.

A commercial aqueous sodium silicate solution (8.90% Na20, 28.7% Si02) was diluted with water to 21.5% Si02 and heated to 70'C to facilitate spraying. A hot air stream was directed into the mixer while silicate was 20 being sprayed onto the showering material and the bed. The resulting agglomerated material was scalped of the particles greater than 2 mm and dried in a fluid bed dryer at 350C for 30 minutes.

A portion of the agglomerated material was put back into the rotary drum and was sprayed with more of the aqueous silicate solution scalped of the plus 2 millimeter material and dried under the same conditions.

Sieve analaysis of the initial materials indicated 70% of the sodium carbonate was between 100 and 200 25 Rm; 70% of the borate salt was less than 44 jim and 70% of the NaDCC.2H20 was between 200 and 600 Jim.

Both the single and double agglomerated materials were evaluated for bleach safety (Localized Dye Attack Test) and storage stability. As shown in Table 1, the double agglomerated material was clearly superior to the single agglomerated material in both respects.

The samples were also evaluated using the Tea Stain Removal Test using cotton and polyester-cotton blends (PE Blend). The results are shown in Table 11. Comparison tests were made using detergent alone (Blank), a composition containing N-H compound as described in U.S. Patent No. 4,279,764 (Comparative), and the detergent plus NaDCC.2H20 (No Coating).

Table 11 clearly shows the superiority of both the double coated and the single coated agglomerates compared with a detergent alone (Blank was run in duplicate) or the agglomerated material of U.S. Patent 35 No. 4,279,764 (Comparative). At 16 mg/I available chlorine, there is evidence that the extra sodium carbonate sodium silicate, and sodium borate compounds provide an added detergency to improve the performance of the double coated material compared with the single coated material. At higher level (32 mg/1) of available chlorine, there is an indication that the added boric acid salt mitigates the hypochlorite activity. This eff ect is noted in spite of the increased detergency of the double agglomerated material, thereby indicating, that if used in excess of the suggested level, the double agglomerated material is unlikely to cause as much fabric damage as the single agglomerated material.

Example 2

Single coated agglomerates were prepared using different sodium polyborate salts, such as disodium 45 tetraborate pentahydrate (Borax-5 Mol) and disodium octaborate tetrahydrate blended with Borax 5-Mol (Borax Blend). These agglomerates were compared using the localized dye test and the results are presented in Table Ill.

For comparative purposes, a dry blend was also evaluated. The dry blend (Dry Blend) contained 32.7% soda ash, 17.9% sodium dichloroisocyanurate dihydrate, 8.9% disodium octaborate tetrahydrate, and 40.5% 50 hydrous sodium silicate (mol ratio 3.22). The Dry Blend corresponded to the double agglomerated composition of Example 1 which had an overall rating of 5.

4 GB 2 148 340 A 4 TABLE 1

Comparison of Single and Double Coated Agglomerates Coating Single Double Dye Attack No. 3.5 5.0 Stability after:

10 days at ambient 98.4% 100% 10 temperature 13 days at ambient 95.4% 100% temperature 240 days at ambient ND 85% temperature 15 510 days at ambient ND 70% temperature Assay:

Sodium Carbonate 39.9% 32.7% 20 NaDCC.21-120 21.8% 17.9% Disodium Octaborate Tetrahydrate 10.9% 8.9% Sodium Silicate & Moisture 27.4% 40.5% 25 ND - Not Determined TABLE 11

Tea Stain Removal Test A vail. Tea Stain Removal Chlor. 68 mgIl Hardness 136mg11 Hardness mgII Cotton PEBlend Cotton PE Blend Blank 6.0 0.4 5.4 -0.3 Blank - 4.5 -0.6 1.2 -3.9 40 Comparative 16 5.3 -1.4 6.4 -2.1 Single Coating 16 12.7 3.0 10.1 2.6 45 Double Coating 16 14.0 3.4 9.1 0.5 No Coating 16 12.2 3.5 9.7 -0.1 so Comparative 32 12.5 3.7 11,5 2.3 Single Coating 32 16.5 11.8 15.0 10.9 55 Double Coating 32 17.0 10.3 14.0 8.9 No Coating 32 18.1 10.8 16.1 8.6 GB 2 148 340 A 5 TABLE Ill

Localized Dye Attack Using Different Borates Sample Extent Intensity Rating 5 Borax-5 Mol 2 3 2.5 Metaborate 3 3 3.0 10 Borax Blend 5 4 4.5 Dry Blend 2 1 1.5

Claims

1. A bleach composition which reduces localized attack on fabrics and dyes byavailabie halogen characterized by particles of a halogen bleaching agent having at least one Whalo atom capable of releasing a hypohalite ion to an aqueous solution, said particles coated with sufficient soluble, hydrated silicate-bound inorganic salt in admixture with a soluble alkali metal salt of boric acid, whereby ratio of the Whalo atoms to 20 the boron atoms in the composition ranges from 0.5A to 10: 1.

2. The composition of claim 1 characterized in that the halogen bleaching agent is an isocyanurate bleaching agent having at least one Whalo atom capable of releasing a hypohalite ion.

3. The composition of claim 1 characterized in that the halogen bleaching agent is a chlorinated cyanurate salt or hydrated salt.

4. The composition of claim 1 characterized in that the halogen bleaching agent is sodium dichloroisocya nu rate or a hydrate thereof.

5. The composition of claim 1 characterized in that the alkali metal salt of boric acid is a sodium polyborate.

6. The composition of claim 1 characterized in that the alkali metal salt is selected from the group consisting of disodium tetraborate pentahydrate, disodium tetraborate tetrahydrate, sodium pentaborate pentahydrate, sodium metaborate tetrahydrate, sodium metaborate dihydrate, disodium octaborate tetrahydrate, and mixtures thereof.

7. The composition of claim 4 characterized in that the alkali metal salt is selected from the group consisting of disodium tetraborate pentahydrate, disodium tetraborate tetrahydrate, sodium pentaborate 35 pentahydrate, sodium metaborate tetrahydrate, sodium metaborate dihydrate, disodium octaborate tetrahydrate, and mixtures thereof.

8. The process of preparing astable halogen bleach system providing reduced localized fabric attack characterized by:

(a) forming a dry mix consisting essentially of an N-halo bleaching agent, a soluble hydratable inorganic 40 salt, and a sufficient alkali metal salt of boric acid whereby the mol ratio of Whalo atoms to boron atoms in the composition is between 0.5A and 10: 1, (b) adding with agitation to said dry mix an aqeuous solution of an alkali metal silicate to induce agglomeration thereby producing particles of Whalo bleaching agent coated with a layer containing both a soluble, hydrated, silicate bound inorganic salt and an alkali metal salt of boric acid, and 45 (c) drying the particles from step (b).

9. The process of claim 8 characterized in that a second coating is applied to the N-halo bleaching agent by forming a second dry mix of the particles from claim 8 and adding with agitation to said dry mix an aqueous solution of an alkali metal silicate thereby producing further silicate binding of the soluble, hydrated, inorganic salt and the alkali metal salt of boric acid, and drying the particles.

10. The process of claim 8 characterized in that the N-halo bleaching agent is a chlorinated cyanurate salt or hydrate thereof.

11. The process of claim 8 characterized in that the N-halo bleaching agent is sodium dichloroisocyanu rate or hydrate thereof.

12. The process of claim 8 characterized in that the alkali metal salt of boric acid is a sodium polyborate. 55

13. The process of claim 8 characterized in that the alkali metal salt is selected from the group consisting of disodium tetraborate pentahydrate, disodium tetraborate tetrahydrate, sodium pentaborate pentahy drate, sodium metaborate tetrahydrate, sodium metaborate dihydrate, disodium octaborate tetrahydrate, and mixtures thereof.

14. The process of claim 9 characterized in that the N-halo bleaching agent is a chlorinated cyanurate salt 60 or a hydrate thereof.

15. The process of claim 9 characterized in that the Whalo bleaching agent is sodium dichloroisocyanu rate or hydrate thereof.

6 GB 2 148 340 A 6

16. The process of claim 9 characterized in that the alkali metal salt is selected from the group consisting of disodium tetraborate pentahydrate, disodium tetraborate tetrahydrate, sodium pentaborate pentahydrate, sodium metaborate tetrahydrate, sodium metaborate dihydrate, disodium octaborate tetrahydrate, and mixtures thereof.

Printed in the UK for HMSO, D8818935, 4185, 7102. Published by The Patent Office, 25 Southampton Buildings, London, WC2A lAY, from which copies may be obtained.